Effects of month and age on prolactin concentrations in stallion serum.

This research article discusses how the levels of prolactin – a hormone – in the blood serum of male horses fluctuate due to seasonal changes and the age of the animal. The study shows that prolactin levels are highest during the summer months and in horses that are over 10 years old.

Methodology of the Research

• The researchers measured the concentrations of prolactin in the blood serum of stallions (male horses).
• A newly developed radioimmunoassay was used for this purpose. This method is based on anti-dog prolactin serum and radiolabelled horse prolactin.
• Serum samples were obtained from 444 stallions at a commercial abattoir over a period of one year, from April to the following March.
• The ages of the stallions were estimated by analyzing the eruption and wear patterns of the incisors (front teeth).

Findings of the Study

• The analysis of variance revealed that both the month and age had a significant effect on prolactin levels. There was no interaction detected between these two factors.
• The highest mean concentrations of prolactin were found between the May and August period, with the peak occurring in July.
• The lowest means were found during December and January, which are winter months.
• The lowest prolactin levels were found in stallions that were 5 years old or less. The highest levels were found in stallions that were older than 10 years.

Implications of the Study

• This study indicates that the secretion of the hormone prolactin in stallions is influenced by seasonal changes, similar to mares and other animals that breed seasonally.
• Furthermore, the study shows that prolactin secretion tends to increase as the horse ages.

The study therefore contributes to a better understanding of hormonal changes in horses and how these are influenced by factors such as the seasons and the age of the animal.